The present invention relates to a data transfer control system, an electronic instrument and a data transfer control method.
An interface standard called IEEE 1394 has recently attracted a great deal of attention. Under this IEEE 1394, a bus reset occurs if an electronic instrument is connected anew to the bus, an electronic instrument is removed from the bus, or the number of nodes connected to the bus changes. When a bus reset occurs, the node topology information is cleared and then the topology information is automatically reset. Since this makes it possible to use hot-plugging of the cable in a hot state, it enables general users to freely plug in and remove the cable to the electronic instrument, in the same way as ordinary domestic electric products such as VCRs.
However, various problems are caused by the occurrence of such bus resets. Examples of prior-art techniques of solving these problems are disclosed in Japanese Patent Application Laid-Open No. 2001-177537 and Japanese Patent Application Laid-Open No. 2001-177536.
Even the above-mentioned prior-art techniques, however, might not be able to guarantee normal operation during a bus reset, depending on the specifications of operating systems (OSs) and application programs that will be on the market in the future.
If a direct memory access (DMA) transfer is started by the execution of a command to a hard disk drive (generally speaking: a storage device; more generally speaking: a device) and subsequently a bus reset occurs during the DMA transfer, by way of example, problems might occur, such as a hang-up of the hard disk drive.